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  <title>Document</title>
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  <script>
    const isPalindrome = (str) => {
      let l = 0, r = str.length - 1;
      while (l < r) {
        if (str[l] != str[r]) return false;
        l++;
        r--;
      }
      return true;
    };
    const palindromePairs = (arr) => {
      const res = [];
      for (let i = 0; i < arr.length; i++) {
        for (let j = i + 1; j < arr.length; j++) {
          if (isPalindrome(arr[i] + arr[j])) res.push([i, j]);
          if (isPalindrome(arr[j] + arr[i])) res.push([j, i]);
        }
      }
      return res;
    };
    console.log(palindromePairs(["abcd", "dcba", "lls", "s", "sssll"]));
  </script>
</body>

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